Characteristics and displacement mechanisms of the dispersed particle gel soft heterogeneous compound flooding system

Considering high temperature and high salinity in the reservoirs, a dispersed particle gel soft heterogeneous compound(SHC) flooding system was prepared to improve the micro-profile control and displacement efficiency. The characteristics and displacement mechanisms of the system were investigated via core flow tests and visual simulation experiments. The SHC flooding system composed of DPG particles and surfactants was suitable for the reservoirs with the temperature of 80-110 °C and the salinity of 1×10~4-10×10~4 mg/L. The system presented good characteristics: low viscosity, weak negatively charged, temperature and salinity resistance, particles aggregation capacity, wettability alteration on oil wet surface, wettability weaken on water wet surface, and interfacial tension(IFT) still less than 1×10^(-1) mN/m after aging at high temperature. The SHC flooding system achieved the micro-profile control by entering formations deeply and the better performance was found in the formation with the higher permeability difference existing between the layers, which suggested that the flooding system was superior to the surfactants, DPG particles, and polymer/surfactant compound flooding systems. The system could effectively enhance the micro-profile control in porous media through four behaviors, including direct plugging, bridging, adsorption, and retention. Moreover, the surfactant in the system magnified the deep migration capability and oil displacement capacity of the SHC flooding system, and the impact was strengthened through the mechanisms of improved displacement capacity, synergistic emulsification, enhanced wettability alteration ability and coalescence of oil belts. The synergistic effect of the two components of SHC flooding system improved oil displacement efficiency and subsequently enhanced oil recovery.

CURRENT COLLOIDAL DISPERSION GELS ARE NOT SUPERIOR TO POLYMER FLOODING

The suggestion that the colloidal-dispersion-gel (CDG) process is superior to normal polymer flooding is misleading and generally incorrect. Colloidal dispersion gels, in their present state of technological development, should not be advocated as an improvement to, or substitute for, polymer flooding. Gels made from aluminum-citrate crosslinked polyacrylamides can act as conventional gels and provide effective conformance improvement in treating some types of excess water production problems if sound scientific and engineering principles are respected.

Examination of literature on colloidal dispersion gels for oil recovery

This paper examines literature that claims,suggests,or implies that floods with"colloidal dispersion gels"(CDGs)are superior to polymer floods for oil recovery.The motivation for this report is simple.If CDGs can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker,then CDGs should be used in place of polymer solutions for most/all polymer,surfactant,and ASP floods.In contrast,if the claims are not valid,(1)money spent on crosslinker in the CDG formulations was wasted,(2)the mobility reduction/mobility control for CDG field projects was under-designed,and(3)reservoir performance could have been damaged by excessive loss of polymer,face-plugging by gels,and/or excessive fracture extension.From this review,the clear answer is that there is no credible evidence that colloidal dispersion gels can propagate deep into the porous rock of a reservoir,and at the same time,provide resistance factors or residual resistance factors that are greater than those for the same polymer formulation without the crosslinker.CDGs have been sold using a number of misleading and invalid arguments.Very commonly,Hall plots are claimed to demonstrate that CDGs provide higher resistance factors and/or residual resistance factors than normal polymer solutions.However,because Hall plots only monitor injection pressures at the wellbore,they reflect the composite of face plugging/formation damage,in-situ mobility changes,and fracture extension.Hall plots cannot distinguish between these effects-so they cannot quantify in situ resistance factors or residual resistance factors.Laboratory studiesdwhere CDG gelants were forced through short cores during 2-3 h-have incorrectly been cited as proof that CDGs will propagate deep(hundreds of feet)into the porous rock of a reservoir over the course of months.In contrast,most legitimate laboratory studies reveal that the gelation time for CDGs is a day or less and that CDGs will not propagate through porous rock after gelation.A few cases were noted where highly depleted Al and/or HPAM fluids passed through cores after one week of aging.Details about these particular formulations/experiments were sparse and questions remain about their reproducibility.No credible evidence indicates that the CDG can propagate deep into a reservoir(over the course of weeks or months)and still provide a greater effect than that from the polymer alone.With one exception,aluminum from the CDG was never reported to be produced in a field application.In the exception,Chang reported producing 1-20%of the injected aluminum concentration.The available evidence suggests that some free(unreacted)HPAM and aluminum that was associated with the original CDG can propagate through porous media.However,there is no evidence that this HPAM or aluminum provides mobility reduction greater than that for the polymer formulation without crosslinker.

Gas channeling control with an in-situ smart surfactant gel during water-alternating-CO_(2) enhanced oil recovery

Undesirable gas channeling always occurs along the high-permeability layers in heterogeneous oil reservoirs during water-alternating-CO_(2)(WAG)flooding,and conventional polymer gels used for blocking the“channeling”paths usually suffer from either low injectivity or poor gelation control.Herein,we for the first time developed an in-situ high-pressure CO_(2)-triggered gel system based on a smart surfactant,N-erucamidopropyl-N,N-dimethylamine(UC22AMPM),which was introduced into the aqueous slugs to control gas channeling inWAG processes.The water-like,low-viscosity UC22AMPM brine solution can be thickened by high-pressure CO_(2) owing to the formation of wormlike micelles(WLMs),as well as their growth and shear-induced structure buildup under shear flow.The thickening power can be further potentiated by the generation of denser WLMs resulting from either surfactant concentration augmentation or a certain range of heating,and can be impaired via pressurization above the critical pressure of CO_(2) because of its soaring solvent power.Core flooding tests using heterogeneous cores demonstrated that gas channeling was alleviated by plugging of high-capacity channels due to the in-situ gelation of UC22AMPM slugs upon their reaction with the pre-or post-injected CO_(2) slugs under shear flow,thereupon driving chase fluids into unrecovered low-permeability areas and producing an 8.0% higher oil recovery factor than the conventional WAG mode.This smart surfactant enabled high injectivity and satisfactory gelation control,attributable to low initial viscosity and the combined properties of one component and CO_(2)-triggered gelation,respectively.This work could provide a guide towards designing gels for reducing CO_(2) spillover and reinforcing the CO_(2) sequestration effect during CO_(2) enhanced oil recovery processes.

大庆油田聚驱后油层无碱中相自适应堵调驱实验

大庆油田聚驱后弱碱复合驱扩大现场试验取得了聚驱后进一步提高采收率13.5百分点的较好效果,但体系中碱的存在导致管线、泵产生腐蚀、结垢和采出液出现严重乳化破乳难等问题。同时,由于优势渗流通道的存在,流度控制难,致使体系中聚合物质量浓度高达2500 mg/L。为解决上述问题并实现更大幅度提高采收率,需研发出适用于大庆油田聚驱后油层的高效中相微乳液驱油体系。通过对表面活性剂溶液的界面张力进行测量,初步筛选出能够达到超低界面张力的表面活性剂产品,然后进行中相微乳液体系水溶性评价,并开展了较为完善的油水相态评价,进一步确定中相微乳液体系的最佳盐度(盐的质量分数)及其与油水比的关系,从而研发出无碱中相微乳液配方,并加入预交联颗粒凝胶(PPG)组成无碱中相自适应堵调驱体系。岩心驱替实验结果表明,该体系聚驱后可进一步提高采收率23.3百分点,比常规弱碱复合驱多提高采收率10.1百分点,降低聚合物用量28%。研究成果为大幅提高大庆油田聚驱后油层的采收率提供了理论及实验支撑。

低渗透裂缝型油田调剖用弱凝胶体系室内评价

通过实验室模拟与现场应用分析,详细考察了弱凝胶体系的性能以及在油田中的实际应用效果。实验结果显示,弱凝胶体系的成胶时间从20℃的115.2 min显著减少至70℃的14.9 min,黏度从1560.5 m Pa·s降至1047.2 m Pa·s,体现了温度提高加速化学交联反应的效果。在老化稳定性实验中,凝胶黏度在室温条件下经过3个月从初始的1200 m Pa·s缓慢降至1149 m Pa·s,而在80℃的高温条件下,从1013 m Pa·s降至970 m Pa·s,表明温度的升高加速了老化过程,但整体上凝胶展示了良好的稳定性。剪切稳定性测试中,凝胶黏度从500 r·min^(-1)的1198 m Pa·s降至5000 r·min^(-1)的987 m Pa·s,显示出良好的剪切稳定性。大洼油田采用弱凝胶调驱技术后,油井的日产油量平均提升了50%,同时减少了水窜现象,优化了油水分层,显著提高了油田的整体采收效率。

“凝胶+颗粒”复合增效调驱体系在蓬莱油田水平井中的应用

蓬莱油田是多套油水系统的岩性油藏,储层以中高孔渗为主,含水率上升迅速。该区块水平井组厚度大,注采优势通道明显。但该区块限压低,且注入水与常规调堵体系的配伍性差,对调驱体系的注入性和封堵性的要求高。本文选用粒径可控、自聚集性能良好的分散微冻胶,配合优选的低阻高强度乳液型聚合物凝胶体系,经实验优化,建立注入性好、封堵性强的“凝胶+颗粒”复合增效调驱体系。在蓬莱油田J井组应用该调驱体系复合增效效果良好,累计增加采油量达7806 m^(3)。

“堵/调/驱”一体化提高采收率实验研究——以渤海Q油田为例

为实现海上油田高效开发,该文针对渤海油藏环境,利用布什黏度计、扫描电镜和岩心驱替装置等开展了封堵体系优选、调驱体系基本性能和驱油效果的评价,并对比堵水、调剖、调驱单独施工和“堵水/调剖/调驱”一体施工的区别。研究表明,“无机+有机”复合凝胶体系初始黏度低,成胶强度高,注入性能和封堵性能良好,含水率≥30%;表面活性剂H1浓度>800 mg/L时,稠油乳化降黏率超过80%。与分别实施“堵水、调剖和调驱”措施相比较,“堵/调/驱”一体实施降水增油效果显著,并且总注入量小,开发时间短,施工费用低,技术经济指标更优。

基于低渗油藏裂缝型水淹泡沫复合调驱技术研究

针对裂缝型油藏水窜水淹以及传统的泡沫体系调控效果受限的问题,提出凝胶-泡沫复合调驱技术,并对其注入工艺进行优化研究。通过室内驱替实验对封堵增油效果进行评价,在此基础上,通过实验设计分别对体系的注入量、注入浓度、注入速度和注入方式进行优化,并进行矿场实践应用。实验结果表明,与单纯水驱相比,凝胶-泡沫体系最终采收率提高幅度达到19.7%。参数优化结果表明,当气液比为3∶1,起泡效果最好;注入量为0.3 PV、注入浓度为900 mg·L^(-1)·PV-1时,驱替效果最优;同时采取小排量、多段塞交替注入方式,驱油效率增幅比笼统注入方式下高6.79%。井场实践结果表明,措施后单井平均日增油1.59 t,含水率降低24.74%,增油率达到56.58%,降水增油效果显著。凝胶-泡沫协同调驱技术能够显著实现高含水井以及低效井降水增油的目的,针对裂缝型油藏注水开发中后期出现水淹水窜问题具有较好的治理效果。

聚合物驱及相关化学驱进展

对国内外聚合物驱及相关化学驱提高采收率技术的近期进展作了综述和讨论。共分 3个论题 :①聚合物驱及驱油聚合物 (HPAM和多糖 ) ;②二元 (SP)和三元 (ASP)复合驱 ;③弱凝胶 (及CDG)调驱。

多段塞复合凝胶调驱技术研究与应用

针对大港油田地层中大孔道普遍存在、封堵难度大的情况,进行了水井深部调驱技术的深化研究与应用。在已开发的预交联凝胶颗粒、地下交联凝胶、橡胶颗粒等调驱剂的基础上,研究应用了多段塞复合凝胶调驱体系,提高了对地层中大孔道的封堵强度,取得了较好的治理效果。2001年以来应用以多段塞复合凝胶体系为主体的工艺实施深部调驱193井次,有效率81.3%,累计增油17.53×104t。为注水开发油田的后期挖潜探索了有效途径,具有广阔的应用前景。

聚合物驱后凝胶与表面活性剂交替注入驱油效果

为开采聚合物驱后油藏剩余油,进一步提高采收率,分析凝胶调剖与表面活性剂驱油结合机理,采用小段塞多轮次交替注入方式;利用铬离子凝胶体系和RMA-1型表面活性剂,在大平板岩心上进行聚合物驱后凝胶与表面活性剂段塞驱油实验.结果表明:利用聚合物驱后凝胶与表面活性剂多轮次交替注入方式驱油后,其阶段采收率可在聚驱基础上提高10%以上,说明凝胶与表面活性剂交替注入驱油技术能够在聚合物驱后进一步挖掘剩余油,提高原油采收率.

改性淀粉凝胶与三元复合驱体系的组合调驱研究

采用双层非均质岩心模型,将调剖和驱油结合,评价不同级差条件下8种开发方案提高采收率的效果。结果表明,岩心渗透率为30×10-3/1000×10-3μm2时,单独聚合物驱和三元驱使含水率下降约15%,采收率分别提高6.7%和8.3%。用改性淀粉凝胶封堵后,三元驱岩心含水率下降至44%,明显低于聚合物驱和水驱的最低含水率60%、70%,三元驱、聚合物驱及水驱采收率增幅分别为23.5%、19.2%和10.1%。三元驱能有效启动低渗层位,三元复合驱对低渗层位剩余油的开采效果明显好于聚合物驱。"改性淀粉凝胶体系+三元复合驱"组合调驱采收率增幅为40.4%,好于二者单独作用时的采收率增幅加和35.6%,并比"铬凝胶+三元复合驱"组合调驱采收率增幅高4.3个百分点。岩心渗透率为30×10-3/2000×10-3μm2和30×10-3/500×10-3μm2时,"改性淀粉凝胶体系+三元复合驱"组合调驱采收率增幅分别为45.3%和34.4%,三元驱提高采收率25.1%和22.2%,油藏非均质性越严重,该组合调驱体系开采效果越好。

聚合物微凝胶组合驱油效果实验研究

使用双管并联长岩心填砂模型和五点法层间非均质模型,模拟研究聚合物溶液和微凝胶体系的流动特征、分流作用和剖面调整能力,探讨微凝胶与低浓度聚合物交替段塞组合的调驱性能和驱油效果,为提高采收率组合驱油方法提供实验依据和理论指导。

低浓度微凝胶体系动态成胶及驱油试验

使用长岩心渗流试验装置 ,模拟油藏条件开展微凝胶体系动态成胶和驱油试验 ,研究了低浓度微凝胶体系在长岩心填砂模型中的动态成胶特征、流动特性和驱油效果。试验结果证明 :低浓度微凝胶体系在通过长岩心的流动过程中能够形成一定强度的微凝胶 ,产生的流动阻力比相同浓度甚至高浓度聚合物溶液高 ;微凝胶体系在岩心内部成胶后 ,具有良好的流动性和传播性 ,在后续水驱过程中 ,仍然保持较高的剩余流动阻力。低浓度微凝胶溶液在动态成胶过程中具有明显的驱油作用 ,可以较大幅度提高石油采收率 ,但微凝胶驱的增油效果主要出现在后续水驱阶段。

稠油油藏高温凝胶改善蒸汽驱开发效果可视化实验

针对稠油油藏蒸汽驱汽窜现象严重的问题,为了研究高温凝胶改善稠油注蒸汽开发的效果,利用二维可视化物理模拟设备,通过图像采集系统对比了注入高温凝胶前、后的图像,并全程跟踪了蒸汽驱开发稠油时汽窜产生的过程以及注高温凝胶后蒸汽驱油层的波及情况,据此研究了利用高温凝胶改善蒸汽驱开发效果的微观机理。实验结果表明:稠油蒸汽驱过程中,由于压力梯度的差异,注采井间容易形成窜流通道;蒸汽在油层中产生明显的指进现象,从而降低蒸汽的波及范围,窜流通道两侧存有大量的剩余油;凝胶溶液首先进入窜流通道,并占据颗粒间的大孔隙,成胶之后对高渗通道有良好的封堵作用;后续注入的蒸汽绕过主流通道,能够进一步驱出剩余油。驱油结果表明:注入凝胶之后的最终波及效率能够达到70.44%,最终驱油效率达到60.45%,分别比单纯蒸汽驱提高了22.35%和15.17%。

抗温疏水缔合聚合物弱凝胶调驱剂室内研究

针对新疆石南4井区三工河组油藏，在84℃考察了组分用量对有机交联疏水缔合聚合物AP-P4弱凝胶成胶性能，主要是48小时表观黏度的影响。成胶液用矿化度9．34g／L、含Ca^2＋336mg／L、含Mg^2＋174m／L的该油藏注入水配制。得到的基础配方为：AP—P41500～1800nag／L＋乌洛托品350mg／L＋苯酚300mg／L＋间苯二酚40mg/L，加入间苯二酚可缩短成胶时间。聚合物浓度为1500和1800mg／L的成胶液，在84℃放置15～30天后黏度达到最高，180天后黏度为最高值的1／2左右，且不脱水；强力剪切不影响成胶后的黏度及其老化稳定性；在岩心内成胶并在84℃老化180天后，岩心渗透率仅略有增大。注入0.3和0．5PV成胶液使水驱后岩心的采收率分别增加24．77％和34．9l％，如弱凝胶注入后在岩心内在84℃老化180天，则采收率增值略有增大，分别增加27．18％和36．45％。该弱凝胶在多孔介质内有良好的高温老化稳定性。图2表4参1。

聚合物驱后油藏提高采收率技术研究

根据室内实验和现场试验效果分析了聚合物驱后油藏进一步提高原油采收率的技术潜力。室内驱油实验表明,聚合物+表面活性剂二元复合驱提高采收率为17.6%～20.1%,提高采收率幅度高于单一表面活性剂驱(3%左右)和单一聚合物驱(11%～15%),高于表面活性剂驱和聚合物驱二者之和,优于同等经济条件下聚合物驱的效果。孤岛中一区Ng3-6和孤东六区聚合物注入完成后接着实施二元复合驱,综合含水进一步下降,日产油量明显增加。聚合物溶液中加入粘弹性颗粒PPG(Preformed Particle Gel)后,体系从偏粘性转变为偏弹性,具有较强的剖面调整能力。2009年2月在聚合物驱转后续水驱多年的孤岛中一区Ng3单元实施聚合物+PPG驱,注入压力上升了1.4MPa,油层纵向非均质性明显改善,纵向各层吸水趋于均匀。

大庆油田聚驱后油藏内源微生物激活剂的筛选和效果评价

聚合物驱油后的油藏含水大幅回升,操作成本高,传统化学方法很难继续提高采收率,而内源微生物采油技术是最有希望的接替技术之一.针对大庆油田聚驱后油藏,利用分子生态学技术考察目标油藏的菌群结构,并通过统计学方法对内源微生物激活剂进行筛选和效果评价.结果表明目标油藏具有多种采油功能微生物,确定以糖蜜,硝酸盐,磷酸盐及酵母粉为主的激活剂体系,该体系能显著提高内源微生物的数量,有益菌浓度提高1～3个数量级,代谢产生的表面活性剂能将原油完全乳化分散,形成稳定的悬浊液,同时也能兼顾厌氧微生物的生长及产甲烷菌代谢产甲烷,因此具备实施内源微生物采油的潜力.

提高底水油藏采收率的综合处理技术

通过底水油藏模型试验,研究了在注水井进行弱凝胶调驱、在生产井注入堵剂隔板,以及在注水井进行弱凝胶调驱的同时在生产井注入堵剂隔板的综合处理对采收率的影响。进行弱凝胶调驱、采取堵剂隔板及综合处理时提高采收率分别约为20%,25%和30%。试验结果表明,综合处理技术抑制底水锥进提高采收率的效果好于任何一种措施单独作用的效果,是一种抑制底水水侵的有效措施,在底水油藏提高采收率中将会有广泛的应用前景。